JP2008117597A - Transparent conductive board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent conductive board with a transparent conductive film with high conductivity through improvement of crystallinity while retaining high carrier concentration of tin-added indium oxide. <P>SOLUTION: The transparent conductive board is made by arranging a transparent base material and a transparent conductive film made of tin-added indium oxide on one face of the transparent conductive film. The transparent conductive film has a concentration gradient with an addition concentration of tin getting higher as it gets away from a transparent base board side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transparent conductive substrate and a manufacturing method thereof.

  The transparent conductive substrate is formed with a transparent conductive oxide (TCO) such as tin-doped indium oxide (ITO), tin oxide (TO), or fluorine-doped tin oxide (FTO) on the surface of glass as an insulator. By doing so, the substrate has conductivity, and has the property of flowing electricity while maintaining the optically transparent property. Among these, ITO is widely known as a transparent conductive film, and is applied to liquid crystal displays such as personal computers, televisions, and mobile phones, and transparent electrodes of solar cells (for example, see Patent Document 1).

ITO has a high carrier concentration due to a large amount of oxygen vacancies, and a high carrier concentration can be obtained even when the amount of tin doped is large. However, if the amount of tin doped is too large, the carrier will be high but the crystallinity will be poor. When the crystallinity is deteriorated, the conductivity is lowered, which is generally not preferable as a transparent conductive substrate (see, for example, Patent Document 2).
Japanese Patent No. 2516688 JP-A-2005-244128

The present invention has been devised in view of such conventional circumstances, and improves the crystallinity of tin-added indium oxide while maintaining a high carrier concentration, and includes a transparent conductive film having high conductivity. It is a first object to provide a conductive substrate.
In addition, the present invention provides a transparent conductive film made of tin-doped indium oxide having good crystallinity on a transparent substrate while maintaining a high carrier concentration even when the tin doping amount is increased. A second object is to provide a method for manufacturing a conductive substrate.

The transparent conductive substrate according to claim 1 of the present invention is a transparent conductive substrate comprising a transparent base material and a transparent conductive film made of tin-added indium oxide on one surface of the transparent base material, The transparent conductive film has a concentration gradient such that the concentration of tin added increases as the distance from the transparent substrate side increases.
The transparent conductive substrate according to claim 2 of the present invention has a portion made of indium oxide to which tin is not added on the side in contact with the transparent base material of the transparent conductive film according to claim 1. It is characterized by.
The transparent conductive substrate according to claim 3 of the present invention is characterized in that, in claim 1, the total amount of tin added in the transparent conductive film is in the range of 2% to 10%.
The manufacturing method of the transparent conductive substrate of Claim 4 of this invention is a manufacturing method of the transparent conductive substrate which forms the transparent conductive film which consists of tin addition indium oxide on one surface of a transparent base material, Comprising: Said transparent When forming the conductive film, the concentration of tin contained in the raw material solution is controlled so that the concentration of tin added increases as the distance from the transparent substrate side increases.
The method for producing a transparent conductive substrate according to claim 5 of the present invention is the method according to claim 4, wherein in the formation of the transparent conductive film, oxidation is performed in which tin is not added to a side of the transparent conductive film in contact with the transparent substrate. A portion made of indium is formed.
According to a sixth aspect of the present invention, in the method for producing a transparent conductive substrate according to the fourth aspect, the transparent conductive film is formed by a spray pyrolysis method.

In the present invention, since the transparent conductive film made of tin-added indium oxide has a concentration gradient so that the concentration of tin added increases as the distance from the transparent substrate side increases, the crystal can be maintained while maintaining a high carrier concentration. Deterioration can be suppressed. As a result, it is possible to provide a transparent conductive substrate provided with a transparent conductive film having high electron mobility and improved conductivity.
Further, in the present invention, when forming a transparent conductive film made of tin-added indium oxide, the concentration of tin added increases as the distance from the transparent substrate side increases by controlling the concentration of tin contained in the raw material solution. Can be controlled. As a result, a transparent conductive substrate capable of forming a transparent conductive film made of tin-doped indium oxide having good crystallinity on a transparent base material while maintaining a high carrier concentration even when the tin doping amount is increased. The manufacturing method of can be provided.

  Hereinafter, an embodiment of a transparent conductive substrate according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a transparent conductive substrate according to the present invention.
The transparent conductive substrate 10 is generally composed of a transparent base material 11 and a transparent conductive film 12 made of tin-added indium oxide (ITO) formed on one surface 11a thereof.

  As the transparent base material 11, a substrate made of a light-transmitting material is used, and any material can be used as long as it is usually used as a transparent base material such as glass, polyethylene terephthalate, polycarbonate, and polyethersulfone. . The transparent substrate 11 is appropriately selected from these. Moreover, as a transparent base material 11, the board | substrate which is as excellent in a light transmittance as possible is preferable on a use, and the board | substrate whose transmittance | permeability is 90% or more is more preferable.

The transparent conductive film 12 is made of ITO, and is a thin film formed on one surface 11a in order to impart conductivity to the transparent substrate 11.
And the transparent conductive substrate 10 of this invention has the density | concentration gradient so that the addition density | concentration of tin may become high as the said transparent conductive film 12 leaves | separates from the transparent base material 11 side.
Thereby, the fall of the crystallinity of ITO can be suppressed, maintaining a high carrier concentration. Thereby, the electron mobility in the transparent conductive film 12 becomes high, As a result, the electroconductivity of the transparent conductive substrate 10 can be improved.

For example, when the transparent conductive substrate of the present invention is used as a working electrode of a photoelectric conversion element, the amount of tin added in the vicinity of the interface with the porous oxide semiconductor layer formed on the transparent conductive film increases the amount of transparent conductive A good ohmic contact can be obtained between the film and the porous oxide semiconductor layer, and the amount of tin doped in other regions is small, which is preferable because a good crystalline film is obtained.
In addition, the addition concentration of tin in the transparent conductive film 12 may change stepwise or may change continuously.

Moreover, as shown in FIG. 2, the transparent conductive substrate 10 of this invention may have the site | part 12a which consists of indium oxide to which tin is not added in the side which contacts the said transparent base material of the said transparent conductive film. .
By forming the portion 12a made of indium oxide having higher crystallinity than tin-added indium oxide in the lower layer, a decrease in crystallinity can be more reliably suppressed. Thereby, the electron mobility in the transparent conductive film 12 can be further increased, and as a result, the conductivity of the transparent conductive substrate 10 can be further improved.

  The total amount of tin added in the transparent conductive film 12 is preferably in the range of 2% to 10%. If the addition concentration of tin is less than 2%, the effect of increasing the carrier concentration due to the addition of tin cannot be sufficiently obtained. On the other hand, when the addition concentration of tin exceeds 10%, the crystallinity of ITO is lowered. By making the addition concentration of tin 2 to 10%, the range of 2% or more and 10% or less reduces the crystallinity within the range in which the amount of tin added maintains a high electron mobility state. Can be suppressed. Further, the current input to the transparent conductive film can be uniformly diffused throughout the film.

Next, the manufacturing method of the transparent conductive substrate 10 of this embodiment is demonstrated.
In this embodiment, first, the transparent conductive film 12 is formed so as to cover the entire area of the one surface 11a of the transparent base material 11, and the transparent conductive substrate 10 is manufactured.
The method for forming the transparent conductive film 12 is not particularly limited, and examples thereof include thin film forming methods such as sputtering, CVD (chemical vapor deposition), spray pyrolysis (SPD), and vapor deposition. Can be mentioned.

Among them, the transparent conductive film 12 is preferably formed by a spray pyrolysis method. By forming the transparent conductive film 12 by a spray pyrolysis method, the concentration of tin added can be easily inclined continuously.
In addition, the spray pyrolysis method is preferable because it does not require a decompression system and can simplify the manufacturing process and reduce costs.

Here, FIG. 3 is a schematic view showing an example of a film forming apparatus used for manufacturing the transparent conductive substrate according to the present invention.
The film forming apparatus 50 is a film forming apparatus that forms a thin film (transparent conductive film 12) on a target object (transparent base material 11) by spray pyrolysis, and is a support means for mounting the target object. 51, temperature control means for adjusting the temperature of the object to be processed, discharge means 54 for spraying the mist 53 made of the raw material solution of the thin film toward one surface of the object to be processed, and the raw material solution. And at least a hood 57 disposed so as to enclose a space 56 between the object to be processed disposed at a position facing the discharge means 54.

The support means 51 has a built-in temperature control means 52 having functions of heating, holding, and cooling the object to be processed 2 in order to form a thin film while keeping the film formation surface 11a of the transparent substrate 11 at a predetermined temperature. Yes. The temperature control means 52 is a heater, for example.
Examples of the concentration control means 55 include a solution mixing method and a mist mixing method.

  The discharge means includes a first introduction path 54α for taking in air (indicated as Air) and a second introduction path 54β for taking in the raw material solution whose tin addition amount has been adjusted by the concentration control means 55. For example, air is introduced in the direction of the arrow α and the raw material solution is introduced in the direction of the arrow β, and these are mixed to form a mist, and then sprayed toward the transparent substrate 11 as the object to be processed through the discharge port 54a. To do.

  Further, in the film forming apparatus 50, the hood 57 is disposed so as to wrap up the space between the object to be processed disposed at a position facing the discharge unit 52, so that the spray form is formed from the discharge port 54 a of the discharge unit 54. The raw material solution sprayed on can be stably kept sprayed in the radial space from the discharge port 54a toward the object to be processed without being affected by the outside air. In other words, the hood 57 also functions to prevent the raw material solution from splashing from the internal space to the outside of the apparatus and increasing the amount of uselessness, thereby effectively using the raw material solution for forming a thin film.

When the transparent conductive film 12 is formed on the transparent substrate 11 by spray pyrolysis using such a film forming apparatus, the film forming conditions, specifically, the concentration of tin contained in the raw material solution is controlled. By doing so, the transparent conductive film 12 is formed so as to have a concentration gradient so that the addition concentration of tin differs, specifically, as the distance from the transparent substrate side increases, the addition concentration of tin increases.
Thereby, the fall of the crystallinity of ITO can be suppressed, maintaining a high carrier concentration. As a result, a transparent conductive film having high crystallinity and high electron mobility can be easily formed.

In forming the transparent conductive film 12, a portion 12a made of indium oxide to which tin is not added may be formed on the side of the transparent conductive film 12 in contact with the transparent base material 11.
By forming the portion 12a made of indium oxide having higher crystallinity than tin-added indium oxide on the side in contact with the transparent substrate 11, a transparent conductive film having higher crystallinity can be formed.

  Since the transparent conductive substrate 10 obtained as described above has a concentration gradient in the transparent conductive film 12 made of ITO so that the addition concentration of tin increases as the distance from the transparent base material side increases, it is high. While maintaining the carrier concentration, it is possible to suppress a decrease in the crystallinity of ITO. As a result, the electron mobility in the transparent conductive film 12 is increased, and the conductivity is improved.

  As mentioned above, although the transparent conductive substrate of this invention and its manufacturing method were demonstrated, this invention is not limited to said example, It can change suitably as needed.

  A transparent conductive substrate was manufactured using a film forming apparatus as shown in FIG. All the steps were performed in an air atmosphere.

<Preparation of raw material solution>
First, a starting material for forming an ITO transparent conductive film was prepared as follows.
Indium (III) chloride tetrahydrate (InCl ₃ · 4H ₂ O, Fw: 293.24) 3 and tin (II) chloride dihydrate (SnCl ₂ · 2H ₂ O, Fw: 225.65) For example, the molar ratio of indium and tin was adjusted to 95: 5, and ethanol was added and dissolved so that each concentration was 0.2 mol / L. This prepared the raw material solution which made tin addition density | concentration 5%, and made this the 5th solution.
Similarly, the molar ratio of indium and tin was adjusted to be 99: 1, 98: 2, 97: 3, 96: 4, 94: 6, 93: 7, 92: 8, and 0.2 mol / L. Ethanol was added and dissolved so as to have each concentration. Thereby, the raw material solution which made the tin addition density | concentration 1%, 2%, 3%, 4%, 6%, 7%, 8% was prepared, and these were sequentially set to 1st solution-4th solution, 6th solution- An eighth solution was obtained.

<Example 1>
In this example, the tin addition concentration is increased in the range of 2% to 8% in the film thickness direction by spray pyrolysis using the above raw material solution on a glass substrate (Tempax # 8330) as a transparent substrate. Then, an ITO transparent conductive film was formed.
Specifically, a transparent conductive substrate having an ITO transparent conductive film having a total thickness of 800 nm was prepared by sequentially using 13 ml each of the second solution to the eighth solution having a tin addition concentration of 2% to 8%.
The film formation conditions at this time were a nozzle diameter of 1 mm, a nozzle-substrate distance of 500 mm, a spraying pressure of about 0.1 MPa, and a substrate surface temperature of 350 ° C.

<Example 2>
In this example, the ITO transparent conductive film was formed so that the tin addition concentration increased in the range of 0% to 8% in the film thickness direction. For this reason, in the preparation of the raw material solution, in addition to the first solution to the eighth solution described above, a raw material solution with a tin addition concentration of 0% was prepared and used as a zero solution. In other respects, an ITO transparent conductive film was formed in the same manner as in Example 1.
Specifically, first, 10 ml of the zero solution was used to form a portion made of indium oxide to which no tin was added. Subsequently, a transparent conductive substrate having an ITO transparent conductive film having a total thickness of 800 nm was prepared using 10 ml of the first solution to the eighth solution in order of tin addition concentration of 1% to 8%.

<Comparative Example 1>
In this example, an ITO transparent conductive film having a constant tin addition concentration of 4% in the film thickness direction was formed. The other points were the same as in Example 1.
Specifically, a transparent conductive substrate having an ITO transparent conductive film having a total thickness of 800 nm was prepared using 90 ml of the fourth solution having a tin addition concentration of 4%.

<Comparative example 2>
In this example, the ITO transparent conductive film was formed such that the tin addition concentration increased in the range of 4% to 8% in the film thickness direction. In other respects, an ITO transparent conductive film was formed in the same manner as in Example 1.
Specifically, a transparent conductive substrate having an ITO transparent conductive film having a total thickness of 800 nm was prepared by using 18 ml of the fourth solution to the eighth solution with a tin addition concentration of 4% to 8% in order.

  About the transparent conductive substrate obtained as mentioned above, the resistance value and the transmittance | permeability were measured as an optical characteristic of a transparent conductive film. The resistance value was measured by the four probe method. The transmittance was measured using an ultraviolet spectrophotometer. The results are shown in Table 1.

From Table 1, the following points became clear.
(1) In Comparative Example 2, an ITO film having the same 4% tin addition concentration as in Comparative Example 1 was first formed on the surface of the transparent substrate, and then the ITO addition concentration was increased to 8% in order. A conductive film was formed. However, compared to Comparative Example 1 in which the tin addition concentration was fixed at 4%, the electron mobility was hardly changed and the electric conductivity (specific resistance) was at the same level.
(2) In Example 1, an ITO film having a tin addition concentration of 2% lower than that of Comparative Example 1 was first formed on the surface of the transparent substrate, and then the ITO transparency was increased to 8% in order. A conductive film was formed. According to this configuration, it was found that the electron mobility can be increased and the specific resistance can be reduced as compared with Comparative Example 1.
(3) In Example 2, an ITO transparent conductive film containing no tins was first formed on the surface of the transparent substrate, and then an ITO transparent conductive film having a tin addition concentration increased to 8% in order was formed. . According to this configuration, it was found that the ITO mobility was further increased as compared with Example 1, and an ITO transparent conductive film having a much lower specific resistance was obtained.
From the above results, the ITO transparent conductive films of Examples 1 and 2 have lower sheet resistance and specific resistance than Comparative Example 1, have sufficiently high transmittance, and also have high electron mobility. confirmed.

  The present invention can be applied to a transparent conductive substrate provided with a transparent conductive film made of ITO.

It is a schematic sectional drawing which shows an example of the transparent conductive substrate which concerns on this invention. It is a schematic sectional drawing which shows an example of the transparent conductive substrate which concerns on this invention. It is a schematic sectional drawing which shows an example of the film-forming apparatus used for manufacture of a transparent conductive substrate.

Explanation of symbols

  10 transparent conductive substrate, 11 transparent base material, 12 transparent conductive film.

Claims (6)

A transparent conductive substrate comprising a transparent base material and a transparent conductive film made of tin-added indium oxide on one surface of the transparent base material,
The said transparent conductive film has a concentration gradient so that the addition density | concentration of tin may become high as it leaves | separates from the transparent base material side, The transparent conductive substrate characterized by the above-mentioned.   The transparent conductive substrate according to claim 1, wherein the transparent conductive substrate has a portion made of indium oxide to which tin is not added on a side in contact with the transparent base material.   2. The transparent conductive substrate according to claim 1, wherein the total amount of tin added in the transparent conductive film is in the range of 2% to 10%. A transparent conductive substrate manufacturing method for forming a transparent conductive film made of tin-added indium oxide on one surface of a transparent substrate,
When forming the transparent conductive film, by controlling the concentration of tin contained in the raw material solution, it is controlled so that the concentration of tin added increases as the distance from the transparent substrate side increases A method for manufacturing a conductive substrate.   5. The transparent conductive substrate according to claim 4, wherein in the formation of the transparent conductive film, a portion made of indium oxide to which tin is not added is formed on a side of the transparent conductive film in contact with the transparent base material. Production method.   The method for producing a transparent conductive substrate according to claim 4, wherein the transparent conductive film is formed by a spray pyrolysis method.

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